Listen for fans coming on, as this sounds like overheating issue.
If fans kick in and then stay constant or dont work at all.
The link is for Notebook hardware control, this will monitor the temp among other things (only reference as a guide any software can give you an indication but not exact temp)
Generally if a laptop hits 90c it will auto cutout to stop major hardware failure normal running temp (40-55c upwards depending on use)
http://www.pbus-167.com/
If the machine is overheating it could be due to blocked vents, faulty heatsink, fans not working or incorrect fitting and thermal paste.
In all honesty if this is due to overheat problems, as the machine has been cutting out my strong advice would be to do all the above ESPECIALLY re-apply thermal paste (arctic silver5) to cpu,
it takes about 100-200 hours of use to start to work 100%.
hope this helps, let me know if i can be of further help